Liquid crystal display device

ABSTRACT

A first electrode  14  provided in a liquid crystal display device of a vertical alignment mode includes, for each picture element region, a lower conductive layer  11,  a dielectric layer  12  covering the lower conductive layer  11,  and an upper conductive layer  13  provided on one side of the dielectric layer  12  which is closer to a liquid crystal layer  30.  The upper conductive layer  13  includes an upper layer opening  13   a , and the lower conductive layer  11  includes a lower layer opening  11   a,  thus forming first, second and third regions (R 1,  R 2,  R 3 ) having gradually decreasing electric field strengths. Liquid crystal molecules  30   a  of the liquid crystal layer  30  in an orientation-regulating region T 1  in which the first, second and third regions are arranged in this order in a predetermined direction change the orientation direction thereof so that they are inclined in a single direction in the presence of an applied voltage.

BACKGROUND OF THE INVENTION

The present invention relates to a liquid crystal display device. Morespecifically, the present invention relates to a liquid crystal displaydevice having a wide viewing angle characteristic.

A liquid crystal display device is a flat display device withadvantageous features such as a reduced thickness, a reduced weight, areduced power consumption, etc. However, a problem of a liquid crystaldisplay device is that the appearance of the displayed image variesdepending upon the direction from which it is viewed, i.e., the “viewingangle dependency” is substantial. The substantial viewing angledependency of a liquid crystal display device is primarily due to thefact that liquid crystal molecules having a uniaxial optical anisotropyare uniformly oriented in the display plane.

An effective method to improve the viewing angle characteristic of aliquid crystal display device is to produce a so-called “multi-domainorientation” by forming a plurality of regions of different orientationswithin a picture element region. Various methods have been proposed inthe art to realize a multi-domain orientation. Typical methods, amongothers, for realizing a multi-domain orientation in a liquid crystaldisplay device of a vertical alignment mode include those disclosed inJapanese Laid-Open Patent Publication No. 6-301036 and JapaneseLaid-Open Patent Publication No. 11-258606.

Japanese Laid-Open Patent Publication No. 6-301036 discloses a method inwhich an opening is provided in a counter electrode which opposes apicture element electrode via a liquid crystal layer interposedtherebetween so as to control the orientation direction of the liquidcrystal molecules by utilizing the inclination (bending) of an electricfield in the vicinity of the region where the opening is provided. Aninclination of an electric field means the production of an electricfield component parallel to the substrate plane (the plane of the liquidcrystal layer). Therefore, the direction in which liquid crystalmolecules having a negative dielectric anisotropy (which are in avertical alignment in the absence of an applied voltage) are inclined inthe presence of an applied voltage (i.e., the azimuth angle direction:the direction of the long axis of inclined liquid crystal molecules asit is projected onto the substrate surface) is defined by the electricfield component parallel to the substrate plane. In other words, acomponent of an inclined electric field which is parallel to thesubstrate plane exerts an orientation-regulating force.

Japanese Laid-Open Patent Publication No. 11-258606 discloses that amulti-domain orientation can be obtained by forming a protrusion, adepression or a slit (an opening provided in an electrode) on onesurface of each of a pair of substrates opposing each other via a liquidcrystal layer interposed therebetween (e.g., a TFT substrate and a colorfilter substrate) which is closer to the liquid crystal layer. Witheither one of the methods disclosed in these publications, it ispossible to realize a desirable viewing angle characteristic by usingthe method in combination with an appropriate optical compensation film.

However, a study conducted by the inventor of the present inventionrevealed that the techniques disclosed in the publications above havethe following problems.

With the method of Japanese Laid-Open Patent Publication No. 6-301036,it is difficult to obtain a uniform multi-domain orientation. Moreover,when the value of the voltage applied across the liquid crystal layer ischanged, it takes a relatively long time to complete the change in theorientation according to the change in the voltage value; that is, theresponse speed is slow. It is believed that these problems are caused bythe fact that the orientation-regulating force for achieving amulti-domain orientation (a force for orienting the liquid crystalmolecules in a particular direction) is relatively weak in this method.

The problems as described above do not occur with the method of JapaneseLaid-Open Patent Publication No. 11-258606. It is believed that withthis method, a sufficiently strong orientation-regulating force isobtained, thereby realizing a relatively stable multi-domainorientation. However, this method has the following problems.

First, if the method disclosed in this publication is employed, it isnecessary to provide a protrusion, a depression or a slit on both of thepair of substrates interposing the liquid crystal layer therebetween inorder to achieve a multi-domain orientation, thereby complicating theproduction process of the liquid crystal display device and lowering theproduction efficiency.

In a plasma-addressed liquid crystal display device (hereinafter,referred to as a “PALC”), a thin glass plate (which forms a part of aplasma cell substrate) having a thickness on the order of 10 μm and anarea on the order of 1 m² is arranged on the side of the liquid crystallayer. Therefore, it is difficult to provide a protrusion or adepression on the surface of the plasma cell substrate which is closerto the liquid crystal layer. Moreover, although the thin glass plateitself functions as an electrode (it is sometimes called a “virtualelectrode”), it is not an electrode made of a conductive layer, wherebya slit (an opening provided in an electrode) cannot be provided therein.Therefore, it is very difficult to use the method disclosed in thispublication with PALCs.

With the method of this publication, the orientation-regulating forcecan be increased by miniaturizing an orientation region by narrowing theinterval between adjacent protrusions, depressions or slits, whichdefines the orientation region. However, since the positional precisionof the orientation regions depends directly upon the precision of theattachment of the substrates with each other, the orientation regioncannot be miniaturized excessively.

SUMMARY OF THE INVENTION

In view of the above-mentioned conventional problems, the presentinvention has been devised for the purpose of realizing a liquid crystaldisplay device with a desirable viewing angle characteristic which has asufficiently stable orientation and a sufficiently high response speedand yet can be produced efficiently.

A liquid crystal display device of the present invention includes afirst substrate, a second substrate and a liquid crystal layerinterposed between the first substrate and the second substrate,wherein: a plurality of picture element regions are provided each ofwhich is defined by a first electrode provided on one side of the firstsubstrate which is closer to the liquid crystal layer and a secondelectrode provided on the second substrate so as to oppose the firstelectrode via the liquid crystal layer; the liquid crystal layer is avertical alignment type liquid crystal layer containing a liquid crystalmaterial having a negative dielectric anisotropy; and each of theplurality of picture element regions includes at least oneorientation-regulating region, the orientation-regulating regionincluding a first region in which an electric field applied across theliquid crystal layer by the first electrode and the second electrode hasa first electric field strength, a second region in which the electricfield has a second electric field strength which is smaller than thefirst electric field strength, and a third region in which the electricfield has a third electric field strength which is smaller than thesecond electric field strength, wherein the first, second and thirdregions are arranged in this order in a predetermined direction. Thus,the object described above is achieved.

Alternatively, a liquid crystal display device of the present inventionincludes a first substrate, a second substrate and a liquid crystallayer interposed between the first substrate and the second substrate,wherein: a plurality of picture element regions are provided each ofwhich is defined by a first electrode provided on one side of the firstsubstrate which is closer to the liquid crystal layer and a secondelectrode provided on the second substrate so as to oppose the firstelectrode via the liquid crystal layer; the liquid crystal layer is avertical alignment type liquid crystal layer containing a liquid crystalmaterial having a negative dielectric anisotropy; and each of theplurality of picture element regions includes at least oneorientation-regulating region, the orientation-regulating regionincluding a first region in which the first electrode and the secondelectrode have a first inter-electrode distance therebetween, a secondregion in which the first electrode and the second electrode have asecond inter-electrode distance therebetween which is greater than thefirst inter-electrode distance, and a third region in which the firstelectrode and the second electrode have a third inter-electrode distancetherebetween which is greater than the second inter-electrode distance,wherein the first, second and third regions are arranged in this orderin a predetermined direction. Thus, the object described above isachieved.

Alternatively, a liquid crystal display device of the present inventionincludes a first substrate, a second substrate and a liquid crystallayer interposed between the first substrate and the second substrate,wherein: a plurality of picture element regions are provided each ofwhich is defined by a first electrode provided on one side of the firstsubstrate which is closer to the liquid crystal layer and a secondelectrode provided on the second substrate so as to oppose the firstelectrode via the liquid crystal layer; the liquid crystal layer is avertical alignment type liquid crystal layer containing a liquid crystalmaterial having a negative dielectric anisotropy; the first electrodeincludes a lower conductive layer, a dielectric layer covering the lowerconductive layer, and an upper conductive layer provided on one side ofthe dielectric layer which is closer to the liquid crystal layer; theupper conductive layer includes an upper layer opening for each of theplurality of picture element regions, and the lower conductive layerincludes a lower layer opening for each of the plurality of pictureelement regions; and each of the plurality of picture element regionsincludes at least one orientation-regulating region, theorientation-regulating region including a first region in which theliquid crystal layer is arranged between the upper conductive layer ofthe first electrode and the second electrode, a second region in whichthe liquid crystal layer and the dielectric layer located within theupper layer opening are arranged between the lower conductive layer ofthe first electrode and the second electrode, and a third region inwhich the liquid crystal layer and the dielectric layer located withinthe upper layer opening are arranged between the lower layer opening ofthe first electrode and the second electrode, wherein the first, secondand third regions are arranged in this order in a predetermineddirection. Thus, the object described above is achieved.

Preferably, each of the upper layer opening and the lower layer openinghas a side extending in a direction perpendicular to the predetermineddirection, and a boundary between the first region and the second regionand a boundary between the second region and the third region extendalong the side.

Preferably, a boundary between the first region and the second regionand a boundary between the second region and the third region extend ina direction perpendicular to the predetermined direction.

Preferably, in each of the plurality of picture element regions, onesurface of the first substrate which is closer to the liquid crystallayer is substantially flat.

Preferably, in each of the plurality of picture element regions, theliquid crystal layer has a substantially constant thickness.

Each of the plurality of picture element regions may include a pluralityof orientation-regulating regions, the plurality oforientation-regulating regions having the same direction of arrangementof the first, second and third regions.

Preferably, each of the plurality of picture element regions includes afirst orientation-regulating region in which the first, second and thirdregions are arranged in this order in a first direction, and a secondorientation-regulating region in which the first, second and thirdregions are arranged in this order in a second direction which isdifferent from the first direction.

Each of the plurality of picture element regions may include a pluralityof at least one of the first orientation-regulating region and thesecond orientation-regulating region.

The first direction and the second direction may be opposite to eachother.

More preferably, each of the plurality of picture element regionsfurther includes a third orientation-regulating region in which thefirst, second and third regions are arranged in this order in a thirddirection which is different from the first and second directions, and afourth orientation-regulating region in which the first, second andthird regions are arranged in this order in a fourth direction which isdifferent from the first, second and third directions, wherein the thirdand fourth directions are perpendicular to the first and seconddirections.

Preferably, the first orientation-regulating region and the secondorientation-regulating region share at least one of the first region andthe third region.

Each of the upper layer opening and the lower layer opening may have apolygonal shape or a circular shape, with the lower layer opening beinglocated within the upper layer opening. In such a case, the center ofgravity of the upper layer opening and that of the lower layer openingpreferably coincide with each other in the substrate plane. While theshape of the upper layer opening and that of the lower layer opening maydiffer from each other, they are preferably similar to each other.

The first electrode may be a picture element electrode which is providedfor each of the plurality of picture element regions, and a voltage maybe applied to the first electrode via an active element which isprovided for each of the plurality of picture element regions.

The second electrode may be a single counter electrode which is providedcommonly for the plurality of picture element regions.

The plurality of picture element regions may be arranged in a matrixpattern having rows and columns; the first electrode may be provided asa plurality of electrodes which are arranged in a stripe patterncorresponding to the columns; and the second substrate may include athin dielectric plate, an insulative substrate, and a plurality ofplasma channels which are arranged in a stripe pattern corresponding tothe rows between the thin dielectric plate and the insulative substrate,and the second electrode may be provided as a plurality of virtualelectrodes respectively formed by corresponding regions of the thindielectric plate respectively opposing the plurality of plasma channelswhich are arranged in a stripe pattern.

The upper conductive layer and the lower conductive layer may beelectrically connected to each other.

The functions of the present invention will now be described.

A liquid crystal display device of a vertical alignment mode accordingto the present invention includes a first electrode and a secondelectrode which apply a voltage across liquid crystal molecules having anegative dielectric anisotropy (which are vertically aligned in theabsence of an applied voltage). The orientation direction of the liquidcrystal molecules changes in each picture element region according to anelectric field which is produced in a liquid crystal layer by thevoltage applied between the first electrode and the second electrode,thereby displaying an image.

Each of the plurality of picture element regions includes at least oneorientation-regulating region, the orientation-regulating regionincluding a first region in which an electric field applied across theliquid crystal layer by the first electrode and the second electrode hasa first electric field strength, a second region in which the electricfield has a second electric field strength which is smaller than thefirst electric field strength, and a third region in which the electricfield has a third electric field strength which is smaller than thesecond electric field strength, wherein the first, second and thirdregions are arranged in this order in a predetermined direction.

Such first, second and third regions can be provided by settingdifferent inter-electrode distances between the first electrode and thesecond electrode, for example. The electric field strength distributionas described above can be realized by employing a structure where theorientation-regulating region of each of the plurality of pictureelement regions includes a first region in which the first electrode andthe second electrode have a first inter-electrode distance therebetween,a second region in which the first electrode and the second electrodehave a second inter-electrode distance therebetween which is greaterthan the first inter-electrode distance, and a third region in which thefirst electrode and the second electrode have a third inter-electrodedistance therebetween which is greater than the second inter-electrodedistance. The inter-electrode distance of a region refers to thedistance between a pair of electrodes in the region which substantiallydetermines the strength of the electric field produced therebetween. Apicture element region having such an inter-electrode distancedistribution can be realized by employing the following structure, forexample.

The first electrode includes, for each picture element region, a lowerconductive layer, a dielectric layer covering the lower conductivelayer, and an upper conductive layer provided on one side of thedielectric layer which is closer to the liquid crystal layer. The upperconductive layer includes an upper layer opening, and the lowerconductive layer includes a lower layer opening. The upper conductivelayer and the lower conductive layer are arranged so as to provide afirst region in which the liquid crystal layer in the picture elementregion is arranged between the upper conductive layer of the firstelectrode and the second electrode (this interval defines the firstinter-electrode distance), a second region in which the liquid crystallayer and the dielectric layer located within the upper layer openingare arranged between the lower conductive layer of the first electrodeand the second electrode (this interval defines the secondinter-electrode distance), and a third region in which the liquidcrystal layer and the dielectric layer located within the upper layeropening are arranged between the lower layer opening of the firstelectrode and the second electrode (this interval defines the thirdinter-electrode distance). Thus, in this structure, the distance betweenthe upper conductive layer (a region excluding the upper layer opening)and the second electrode defines the first inter-electrode distance, andthe distance between the lower conductive layer (a region excluding thelower layer opening) and the second electrode defines the secondinter-electrode distance. The third inter-electrode distance is definedby the distance between the opening of the first electrode (a portionwhere the upper layer opening and the lower layer opening overlap witheach other and where no conductive layer is formed) and the secondelectrode, whereby the third inter-electrode distance is infinite.

The inter-electrode distance as used herein is as described above, andwhen at least one of a pair of opposing electrodes has an opening (aregion where no conductive film exists), the inter-electrode distance ofthe region corresponding to the opening is infinite. The “firstelectrode” and the “second electrode” as used herein are electrodeswhich define a picture element region, and are members having a functionof producing an electric field in the liquid crystal layer so as tochange the orientation of the liquid crystal layer, thereby producing adisplay. Each of the “first electrode” and the “second electrode” mayinclude not only a single conductive layer but also a plurality ofconductive layers separated from one another by a dielectric layer.Moreover, each conductive layer may include an opening.

The functions of a liquid crystal display device of the presentinvention will be described by illustrating, for example, anorientation-regulating region formed by the first electrode (having theupper conductive layer and the lower conductive layer) and the secondelectrode.

The strength of an electric field produced in the liquid crystal layerof the first region is directly influenced primarily by the potentialdifference between the upper conductive layer and the second electrode,and the strength of an electric field produced in the liquid crystallayer of the second region is directly influenced by the potentialdifference of a liquid crystal layer portion which is obtained bydivision (primarily capacitance division) of the potential differencebetween the lower conductive layer and the second electrode by thedielectric layer and the liquid crystal layer. Therefore, the strengthof the electric field applied across the liquid crystal layer by thefirst electrode and the second electrode can be easily made smaller inthe second region than in the first region. As a result, in the vicinityof the boundary between the first region and the second region, aninclination (bending) of an electric field occurs. As described above,an inclination of an electric field means the production of an electricfield component parallel to the substrate plane (the plane of the liquidcrystal layer), and the component parallel to the substrate plane exertsan orientation-regulating force. Thus, an orientation-regulating forceoccurs in the vicinity of the boundary between the first region and thesecond region. The above-described relationship can be realized with,for example, a simple structure where the upper conductive layer and thelower conductive layer are electrically connected to each other.

The liquid crystal layer of the third region is located between thelower layer opening located within the upper layer opening and thesecond electrode, and there are no electrodes (conductive layers)opposing each other which would produce an electric field directlyacross the liquid crystal layer of the third region, whereby the liquidcrystal layer of the third region is influenced by an electric fieldfrom other regions of electrodes (conductive layers) existing around thethird region. Therefore, the strength of the electric field to beapplied across the liquid crystal layer of the third region is smallerthan the strength of the electric field to be applied across the liquidcrystal layer of surrounding regions. As a result, an inclination(bending) of an electric field occurs also in the vicinity of theboundary between the second region and the third region, therebyproducing an orientation-regulating force also in the vicinity of theboundary between the second region and the third region. Since thefirst, second and third regions are arranged in a single direction, thedirection of the orientation-regulating force occurring in the vicinityof the boundary between the first region and the second region and thatoccurring in the vicinity of the boundary between the second region andthe third region are the same, whereby a substantialorientation-regulating force occurs also in the second region whichexists between these boundaries. Of course, the direction of theorientation-regulating force substantially occurring in the secondregion is the same as that of the orientation-regulating force in thevicinity of these two boundary regions. Thus, the first, second andthird regions, arranged in a single direction as a set, serve as asingle orientation-regulating region, wherein the orientation directionof the liquid crystal molecules which are regulated by theorientation-regulating region is the direction of arrangement of thefirst, second and third regions.

At least one orientation-regulating region is provided for each pictureelement region, and in the orientation-regulating region, the first,second and third regions are arranged in this order in a predetermineddirection. Therefore, the strength of an electric field produced in theliquid crystal layer gradually decreases in the predetermined direction.An inclined electric field is produced between the first region and thesecond region, and an inclined electric field is produced between thesecond region and the third region, wherein these inclined electricfields have the same inclination direction in the predetermineddirection. Therefore, the liquid crystal molecules of the liquid crystallayer in the orientation-regulating region change the orientationdirection thereof so that they are inclined in a single direction in thepresence of an applied voltage. As a result, it is possible to obtain asufficiently stable orientation and a sufficiently high response speed.Moreover, this function can be obtained by changing the structure ofonly the first electrode. Therefore, the present invention does notcomplicate the production process and can easily be used with varioustypes of liquid crystal display devices. The predetermined direction inwhich the liquid crystal molecules in the orientation-regulating regionare inclined can be suitably set according to the viewing anglecharacteristic which is required for the liquid crystal display device.

The functions of the present invention have been described in the abovewith respect to a structure where the orientation-regulating regionincludes first, second and third regions. Of course, these functions canbe obtained if the orientation-regulating region includes at least thefirst, second and third regions, and the orientation-regulating regionmay further include a fourth region, a fifth region, and so on, asnecessary. The fourth region is a region with a fourth electric fieldstrength which is smaller than the third electric field strength of thethird region, and the fifth region is a region with a fifth electricfield strength which is even smaller than the fourth electric fieldstrength. The fourth region and the fifth region are arranged in thisorder in the predetermined direction, following the third region. Thus,the first, second, third, fourth and fifth regions, arranged in a singledirection as a set, serve as a single orientation-regulating region,wherein the orientation direction of the liquid crystal molecules whichare regulated by the orientation-regulating region is the direction ofarrangement of the first to fifth regions.

For example, the fourth region has a fourth inter-electrode distancewhich is greater than the third inter-electrode distance, and the fifthregion has a fifth inter-electrode distance which is greater than thefourth inter-electrode distance. Specifically, for example, a furtherdielectric layer is provided under the lower conductive layer (on thesubstrate side) of the first electrode, and a conductive layer (referredto as the “additional conductive layer”) having an opening (referred toas the “additional opening”) is provided under the further dielectriclayer. The additional conductive layer is arranged so that the openingof the additional conductive layer is located within the lower layeropening of the lower conductive layer. In such a structure, a region ofthe liquid crystal layer which is located between a conductive portionof the additional conductive layer (i.e., a portion thereof excludingthe additional opening) and the second electrode (this interval definesthe fourth inter-electrode distance) serves as the fourth region, and aregion of the liquid crystal layer which is located between theadditional opening of the additional conductive layer and the secondelectrode (this interval defines the fifth inter-electrode distance,which in this example infinite) serves as the fifth region.Alternatively, the third region can be formed by providing a dielectriclayer under the lower layer opening defining the third region andfurther providing a conductive layer having no opening under thisdielectric layer (that is, the third inter-electrode distance, which isinfinite in the above example, may be finite). This structure ispreferred because all regions of the liquid crystal layer are sandwichedby conductive layers, whereby the electric field produced in the liquidcrystal layer is less likely affected by an external influence.

Preferably, the boundary between the first region and the second regionand the boundary between the second region and the third region extendin a direction perpendicular to the predetermined direction. Forexample, if one employs a structure where each of the upper layeropening and the lower layer opening has a side extending in a directionperpendicular to the predetermined direction, and the boundary betweenthe first region and the second region and the boundary between thesecond region and the third region extend in parallel to the side of theupper layer opening and the lower layer opening, the directions of theinclined electric fields produced around the respective regionboundaries coincide with each other also in terms of the azimuth angledirection (the direction in the display plane), thereby increasing theorientation-regulating effect.

The orientation-regulating region can be formed by changing thestructure of one of the pair of electrodes opposing each other via theliquid crystal layer (i.e., the first electrode). Therefore, the surfaceof the first substrate (the substrate on which the first electrode isformed) which is closer to the liquid crystal layer can be madesubstantially flat in each of the picture element regions. In otherwords, it is not necessary to provide a protrusion or a depression fordefining the orientation direction of the liquid crystal molecules.Moreover, the thickness of the liquid crystal layer in the pictureelement regions can be made substantially constant. Therefore, theorientation-regulating region according to the present invention can beeasily used with various types of liquid crystal display devices, anddoes not complicate the production process.

It is possible to reduce the area of each orientation-regulating regionby providing in each picture element region a plurality oforientation-regulating regions which regulate the orientation directionof the liquid crystal molecules in the same direction. Thus, it ispossible to improve the response speed of a mono-domain-orientationpicture element region.

For improving the viewing angle characteristic, it is preferred toprovide in each picture element region a plurality oforientation-regulating regions which regulate the orientation directionof the liquid crystal molecules in directions different from oneanother, thereby forming a multi-domain orientation. In such a case, itis possible to reduce the area of each orientation-regulating region byproviding a plurality of orientation-regulating regions which regulatethe orientation direction of the liquid crystal molecules in the samedirection. Thus, it is possible to improve the response speed of thepicture element region of a multi-domain orientation.

The plurality of orientation-regulating regions preferably includeorientation-regulating regions where the directions in which the liquidcrystal molecules are oriented by the orientation-regulating regions(such a direction is also referred to as the orientation direction, theinclination direction or the orientation axis of theorientation-regulating region) are opposite to each other. When aplurality of orientation-regulating regions are provided for eachpicture element region, it is preferred that the orientation-regulatingregions have opposite inclination directions of liquid crystalmolecules, so that the respective viewing angle dependencies of theorientation-regulating regions can be compensated for by each other,thereby efficiently improving the viewing angle characteristic.

Moreover, it is possible to obtain an even more symmetrical viewingangle characteristic by providing four or more orientation-regulatingregions having different inclination directions (orientation axes).Particularly, it is possible to obtain a liquid crystal display devicehaving a high light efficiency in addition to the highly symmetricalviewing angle characteristic, by providing four orientation-regulatingregions respectively having four different inclination directions(orientation axes) so that any two inclination directions selected fromamong the four inclination directions have an angle which is an integralmultiple of about 90° with respect to each other.

When a plurality of orientation-regulating regions which regulate theorientation direction of the liquid crystal molecules in differentdirections are provided in each picture element region (i.e., in thecase of a multi-domain orientation), it is preferred to arrange theplurality of orientation-regulating regions so that at least two of theorientation-regulating regions share the first and second regions so asto obtain a display with a high light efficiency (i.e., a brightdisplay).

Each of the first region and the third region is provided for thepurpose of inclining the electric field along the boundary between thatregion and the second region, i.e., to obtain an orientation-regulatingforce therebetween. The second region is a region in which the liquidcrystal molecules are oriented substantially uniformly due to thisorientation-regulating force, thereby obtaining a substantially uniformamount of transmitted light across the region. Generally, in a liquidcrystal display device, if one employs a structure with which a uniformamount of transmitted light can be obtained across the entire pictureelement region (e.g., a TN type liquid crystal display device), it ispossible to obtain the maximum light efficiency (the highesttransmittance) for the picture element region as a whole (or for thedisplay region of the liquid crystal display device as a whole). Thus,in the case of a liquid crystal display device of the present invention,it is preferred in terms of the light efficiency that the area of theentire picture element region which is occupied by the second region(where a uniform amount of transmitted light can be obtained) isincreased as much as possible, thereby increasing the light efficiency.Accordingly, in order to increase the light efficiency, it is preferredthat the area of the entire picture element region which is occupied bythe first and third regions is reduced as much as possible within suchan extent that a desired orientation-regulating force can be obtained soas to increase as much as possible the area occupied by the secondregion.

It is possible to reduce the area of a picture element region occupiedby the first region and the third region by arranging the plurality oforientation-regulating regions so that the orientation-regulatingregions share at least one of the first region and the third region.Thus, it is possible to improve the light efficiency. When two types oforientation-regulating regions respectively havingorientation-regulating directions opposite to each other (different fromeach other by 180°) are arranged in an alternating pattern, the firstregion and the third region can be shared around boundaries between theorientation-regulating regions. The first region and the third regioncan be shared because the electric field inclination directions, i.e.,the orientation-regulating directions, are opposite to eachother(different from each other by 180°) between the two boundariesrespectively between the first region and the second region and betweenthe third region and the second region.

It is possible to improve the viewing angle characteristic also byorienting the liquid crystal molecules in an axial symmetry. It ispossible to obtain a stable axially symmetrical orientation for exampleby providing an upper layer opening and a lower layer opening eachhaving a polygonal shape or a circular shape, with the lower layeropening being provided within the upper layer opening. When employing apolygonal shape for the openings, it is preferred to employ a regularpolygon in terms of the symmetry. However, it is possible to realize asubstantially axially symmetrical orientation with an irregular polygonby selecting the irregular polygon according to the shape of the pictureelement region, etc.

A sufficient response speed and viewing angle characteristic may beobtained even when a mono-domain structure is employed for each pictureelement region. Since the display signals of adjacent picture elementregions are correlated with each other, it is possible to improve theviewing angle characteristic when the orientation directions of theorientation-regulating regions are different from each other (preferablyperpendicular to each other) between adjacent picture element regions.In the case of a color display device, this can be achieved by employingdifferent orientation directions for adjacent pixel regions, each pixelregion being comprised of R, G and B picture element regions. If apicture element region is small, it is possible to achieve a sufficientresponse speed by providing one orientation-regulating region therein.Moreover, as described above, it is possible to improve the responsespeed of a mono-domain-orientation picture element region by forming aplurality of orientation-regulating regions therein which regulate theliquid crystal molecules in the same direction.

The electrode structure including at least two conductive layers (eachhaving openings therein) with a dielectric layer interposed therebetweencan be used for either the picture element electrodes or the counterelectrode of an active matrix type liquid crystal display device.Moreover, the electrode structure can also be used for the signalelectrodes in a PALC which are arranged to oppose the plasma channelsvia a liquid crystal layer interposed therebetween. Thus, the electrodestructure can be widely used with known liquid crystal display devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram schematically illustrating a cross-sectionalstructure of a liquid crystal display device 100 of one embodiment ofthe present invention along with electric force lines.

FIG. 1B is a diagram schematically illustrating the cross-sectionalstructure of the liquid crystal display device 100 of one embodiment ofthe present invention along with an equipotential line.

FIG. 1C is a diagram schematically illustrating a potential distributionproduced in the vicinity of the interface between a liquid crystal layerand a first electrode of the liquid crystal display device 100 of oneembodiment of the present invention.

FIG. 1D is a plan view schematically illustrating the liquid crystaldisplay device 100 of one embodiment of the present invention.

FIG. 2A is a diagram schematically illustrating a cross-sectionalstructure of a liquid crystal display device 200 of Comparative Examplealong with an equipotential line.

FIG. 2B is a plan view schematically illustrating the liquid crystaldisplay device 200 of Comparative Example.

FIG. 3A is a plan view schematically illustrating a liquid crystaldisplay device 300 of Embodiment 1 of the present invention.

FIG. 3B is a cross-sectional view schematically illustrating the liquidcrystal display device 300 of Embodiment 1 of the present invention.

FIG. 4 is a diagram schematically illustrating a liquid crystal displaydevice 400 of Embodiment 1 of the present invention.

FIG. 5 is a graph illustrating the applied voltage dependency of thetransmittance of the liquid crystal display device 400.

FIG. 6 is an iso-contrast contour curve (contrast ratio=30) of theliquid crystal display device 400.

FIG. 7 is a diagram schematically illustrating a liquid crystal displaydevice 500 of Embodiment 1 of the present invention.

FIG. 8 is a plan view of a counter substrate 600 b used in a liquidcrystal display device of Embodiment 2 of the present invention.

FIG. 9 is a perspective view schematically illustrating a liquid crystaldisplay device 700 of Embodiment 3 of the present invention.

FIG. 10 is a cross-sectional view schematically illustrating the liquidcrystal display device 700 of Embodiment 3 of the present invention.

FIG. 11 is a diagram schematically illustrating the planar structure ofa data electrode 714 of the liquid crystal display device 700.

FIG. 12 is a diagram schematically illustrating the structure of a firstelectrode 814 used in a liquid crystal display device according to thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings. First, theelectrode structure of the liquid crystal display device of the presentinvention and the function thereof will be described.

In the present specification, a region of a liquid crystal displaydevice corresponding to a “picture element”, which is the minimum unitof display, will be referred to as a “picture element region”. In acolor liquid crystal display device, R, G and B “picture elements”correspond to one “pixel”. In an active matrix type liquid crystaldisplay device, a picture element region is defined by a picture elementelectrode and a counter electrode which opposes the picture elementelectrode. In a PALC, a picture element region is defined as a regionwhere one of column electrodes which are arranged in a stripe patterncrosses one of plasma channels which are also arranged in a stripepattern perpendicular to the column electrodes. In an arrangement with ablack matrix, strictly speaking, a picture element region is a portionof each region across which a voltage is applied according to theintended display state which corresponds to an opening of the blackmatrix.

A liquid crystal display device 100 of one embodiment of the presentinvention will be described with reference to FIG. 1A, FIG. 1B, FIG. 1Cand FIG. 1D. FIG. 1A and FIG. 1B are cross-sectional views of the liquidcrystal display device 100, and FIG. 1D is a plan view thereof. FIG. 1Aand FIG. 1B are cross-sectional views both taken along line 1A-1A′ ofFIG. 1D. FIG. 1C schematically illustrates the potential distributionproduced in the liquid crystal layer of the liquid crystal displaydevice 100.

In the following description, the color filter and the black matrix areomitted for the sake of simplicity. In subsequent figures, each elementhaving substantially the same function as that of the liquid crystaldisplay device 100 will be denoted by the same reference numeral andwill not be further described.

The liquid crystal display device 100 includes a first substrate (e.g.,an active matrix substrate) 100 a, a second substrate (e.g., a countersubstrate) 100 b, and a liquid crystal layer 30 provided between thefirst substrate 100 a and the second substrate 100 b. Liquid crystalmolecules 30 a of the liquid crystal layer 30 have a negative dielectricanisotropy, and are oriented by a vertical alignment layer (not shown),which is provided on one surface of each of the first substrate 100 aand the second substrate 100 b which is closer to the liquid crystallayer 30, in a vertical alignment with respect to the surface of thevertical alignment layer in the absence of an applied voltage across theliquid crystal layer 30. Since the surface of the vertical alignmentlayer is substantially parallel to the surfaces of the substrates 100 aand 100 b, the liquid crystal molecules 30 a are also referred to asbeing “vertical to the substrate surface”. In the present specification,the liquid crystal layer 30 in the absence of an applied voltage isreferred to as being in a “vertical alignment”, and the liquid crystallayer 30 is referred to as a “vertical alignment type liquid crystallayer”. However, the liquid crystal molecules 30 a of the liquid crystallayer 30 in the vertical alignment may be slightly inclined from thenormal to the surface of the vertical alignment film (the substratesurface) depending upon the type of the vertical alignment film or thetype of the liquid crystal material being used. Generally, the verticalalignment refers to a state where the liquid crystal molecular axis isoriented at an angle of about 85° or more with respect to the surface ofthe vertical alignment film.

The first substrate 100 a of the liquid crystal display device 100includes a transparent substrate (e.g., a glass substrate) 10 and afirst electrode (e.g., a picture element electrode) 14 which is formedon the surface thereof. The second substrate 100 b includes atransparent substrate (e.g., a glass substrate) 20 and a secondelectrode (e.g., a counter electrode) 22 which is formed on the surfacethereof. The orientation of the liquid crystal layer 30 changes for eachpicture element region according to the voltage applied thereacrossbetween the first electrode 14 and the second electrode 22 which arearranged so as to oppose each other via the liquid crystal layer 30. Adisplay is produced by utilizing a phenomenon that the polarization oflight having passed through the liquid crystal layer 30 changes alongwith the change in the orientation of the liquid crystal layer 30.

The first electrode 14 of the liquid crystal display device 100 includesa lower conductive layer 11, a dielectric layer 12 covering the lowerconductive layer 11, and an upper conductive layer 13 provided on oneside of the dielectric layer 12 which is closer to the liquid crystallayer 30. The lower conductive layer 11 includes a lower layer opening11 a, and the upper conductive layer 13 includes an upper layer opening13 a. They are arranged so that the lower layer opening 11 a is locatedwithin the upper layer opening 13 a. The lower layer opening 11 a andthe upper layer opening 13 a each refer to a portion of the respectiveconductive layers where a conductive film is not formed.

For the sake of simplicity, the second electrode 22 is herein assumed tobe a single film of a conductive material (having no opening within apicture element region) which is formed across the entirety of onepicture element region. However, the second electrode 22, having such astructure as described above and opposing the first electrode 14, is notrequired to have any special structure for obtaining the effects of thepresent invention, and may be one which has a known electrode structure.

The two-dimensional arrangement of the first electrode 14 and the secondelectrode 22 in the display plane will be described. The upper layeropening 13 a of the upper conductive layer 13 is formed so as to includetherein the lower layer opening 11 a of the lower conductive layer 11.Thus, as illustrated in FIG. 1D, the upper layer opening 13 a has awidth (length in the lateral direction of the figure) which is greaterthan that of the lower layer opening 11 a. Preferably, the upper layeropening 13 a and the lower layer opening 11 a have sides parallel toeach other, and the lower layer opening 11 a is arranged to be locatedin the center of the upper layer opening 13 a in the width directionthereof.

The first electrode 14 and the second electrode 22 arranged as describedabove form regions therebetween having different structures.Specifically, the liquid crystal display device 100 includes a firstregion R1 in which the liquid crystal layer 30 is arranged between theupper conductive layer 13 and the second electrode 22, a second regionR2 in which the liquid crystal layer 30 and the dielectric layer 12located within the upper layer opening 13 a are arranged between thelower conductive layer 11 and the second electrode 22, and a thirdregion R3 in which the liquid crystal layer 30 and the dielectric layer12 located within the upper layer opening 13 a are arranged between thelower layer opening 11 a and the second electrode 22.

In the present embodiment, orientation-regulating regions T1 andorientation-regulating regions T2 are arranged in an alternatingpattern. In the orientation-regulating region T1, the first region R1,the second region R2 and the third region R3 are arranged in this orderin a direction L in FIG. 1A and FIG. 1B. In the orientation-regulatingregion T2, the regions R1, R2 and R3 are arranged in this order in adirection −L (opposite to the direction L). The first region R1 and thethird region R3 are arranged so that they are shared by theorientation-regulating region T1 and the orientation-regulating regionT2 adjacent to each other.

The function of the electrode structure of the liquid crystal displaydevice 100 will be described with reference to FIG. 1A, FIG. 1B and FIG.1C.

FIG. 1A schematically illustrates an electric force line EF of anelectric field produced in the liquid crystal layer 30 of the liquidcrystal display device 100 in the presence of an applied voltage, alongwith the change in the orientation direction of the liquid crystalmolecules 30 a. FIG. 1B schematically illustrates an equipotential lineEQ (the cross section of the equipotential surface) of an electric fieldproduced through the liquid crystal layer 30 in the presence of anapplied voltage, along with the change in the orientation direction ofthe liquid crystal molecules 30 a. It is assumed that the absolute valueof the voltage is greater than the absolute value of the thresholdvoltage. Generally, in the present invention, an orientation-regulatingforce from an electric field can be obtained if the relationshipVb≦Va<Vc or Vb≧Va>Vc is satisfied, wherein Va denotes the potentialapplied to the lower conductive layer 11 of the first electrode 14, Vbdenotes the potential applied to the upper conductive layer 13 of thefirst electrode 14, and Vc denotes the potential applied to the secondelectrode 22. A case where a positive voltage is applied to the firstelectrode 14 will be described below while assuming that the secondelectrode 22 is at the ground potential for the sake of simplicity. Itis also assumed that an equal potential is applied to the lowerconductive layer 11 and the upper conductive layer 13 of the firstelectrode 14.

The strength of an electric field produced in the liquid crystal layer30 of the first region R1 is directly influenced primarily by thepotential difference between the upper conductive layer 13 and thesecond electrode 22, and the strength of an electric field produced inthe liquid crystal layer 30 of the second region R2 is directlyinfluenced by the potential difference which is obtained by division(primarily capacitance division) of the potential difference between thelower conductive layer 11 and the second electrode 22 by the dielectriclayer 12 and the liquid crystal layer 30. Therefore, the potentialdifference applied across the liquid crystal layer 30 by the firstelectrode 14 and the second electrode 22 is smaller in the second regionR2 than in the first region R1, whereby the electric field produced inthe liquid crystal layer 30 in the vicinity of the boundary between thesecond region R2 and the first region R1 is inclined.

There are no electrodes (conductive layers) opposing each other whichwould produce an electric field directly through the liquid crystallayer 30 of the third region R3, whereby the liquid crystal layer 30 ofthe third region R3 is influenced by an electric field from otherregions of electrodes (conductive layers) existing around the thirdregion R3. Therefore, the strength of the electric field to be appliedacross the liquid crystal layer 30 of the third region R3 is smallerthan the strength of the electric field to be applied across the liquidcrystal layer 30 of the regions R2 existing around the third region R3,whereby the electric field produced in the liquid crystal layer 30 inthe vicinity of the boundary between the second region R2 and the firstregion R1 is inclined.

As a result, the electric field (electric force line EF) produced in theorientation-regulating region T1 or T2 of the liquid crystal layer 30 ofthe liquid crystal display device 100 is inclined in the vicinity of theboundary between the first region R1 and the second region R2 and in thevicinity of the boundary between the second region R2 and the thirdregion R3 as illustrated in FIG. 1A. The inclination direction is in thedirection in which the first region R1, the second region R2 and thethird region R3 are arranged in this order. Specifically, the electricfield is inclined leftward in the orientation-regulating region T1 andrightward in the orientation-regulating region T2. The liquid crystalmolecules 30 a having a negative dielectric anisotropy are subject to,in the electric field, a torque such as to orient the molecular axisvertically to the direction of the electric field (electric force lineEF), whereby the liquid crystal molecules 30 a are inclined in thevicinity of the boundary between the first region R1 and the secondregion R2 and in the vicinity of the boundary between the second regionR2 and the third region R3 according to the directions of the respectiveinclined electric fields (see arrows in FIG. 1A, FIG. 1B and FIG. 1D).The liquid crystal molecules 30 a are inclined counterclockwise in thefirst orientation-regulating region T1 and clockwise in the secondorientation-regulating region T2.

An electric field substantially vertical to the substrate is produced inthe vicinity of the center of the second region R2 located between thefirst region R1 and the third region R3. Therefore, the liquid crystalmolecules 30 a present in this region are not subject to a torque froman electric field which would incline the liquid crystal molecules 30 ain a particular direction. However, the second region R2 is providedbetween the first region R1 and the third region R3, and the directionof the produced inclined electric field is the same in the vicinity ofthe boundary between the first region R1 and the second region R2 and inthe vicinity of the boundary between the second region R2 and the thirdregion R3, whereby the liquid crystal molecules 30 a therein areaccordingly inclined in the same direction. Therefore, the liquidcrystal molecules present in the vicinity of the center of the secondregion R2 are influenced by the change in the orientation of the liquidcrystal molecules 30 a in the vicinity of the boundaries so as to beinclined in the same direction. In other words, the liquid crystalmolecules 30 a in the vicinity of the boundary between the second regionR2 and the first region R1 and those in the vicinity of the boundarybetween the second region R2 and the third region R3 (which influencethe orientation direction (inclination direction) of the liquid crystalmolecules 30 a present in the vicinity of the center of the secondregion R2 in which the inclination direction is not uniquely regulatedby an electric field) are both inclined in the same direction. As aresult, all of the liquid crystal molecules 30 a are stably inclined inthe same direction within each orientation-regulating region.

FIG. 1C is a diagram schematically illustrating the potentialdistribution along the boundary between the first electrode 14 and theliquid crystal layer 30. The vertical axis denotes the potential, andthe horizontal axis corresponds to the position in FIG. 1A or FIG. 1D.Assuming that the potential of the second electrode 22 is zero (groundpotential), the value of a voltage to be applied across the liquidcrystal layer 30 in each region is equal to the value of the potentialof that region as illustrated in FIG. 1C. Thus, the voltages appliedacross the liquid crystal layer 30 in the respective regions, the firstregion R1, the second region R2 and the third region R3, have values ofV1, V2 and V3, respectively. Therefore, as illustrated in FIG. 1C, thevoltage V2 applied across the liquid crystal layer 30 of the secondregion R2 is lower than the voltage V1 applied across the liquid crystallayer 30 of the first region R1, and the voltage V3 applied across thethird region R3 is even lower than the voltage V2 applied across thesecond region R2. Therefore, the electric field produced in theorientation-regulating region T1 or T2 as represented by theequipotential line EQ is a curve which repeatedly goes up and down in astepped manner as illustrated in FIG. 1B.

The equipotential line EQ illustrated in FIG. 1B is inclined whereadjacent regions have different potentials, i.e., in the vicinity of theboundary between the first region R1 and the second region R2 and in thevicinity of the boundary between the second region R2 and the thirdregion R3. The direction of the potential gradient is in the directionin which the first region R1, the second region R2 and the third regionR3 are arranged in this order (see, for example, arrows in FIG. 1D). Theliquid crystal molecules 30 a having a negative dielectric anisotropyare subject to a torque from an electric field such that the molecularaxis is oriented in parallel to the equipotential line EQ. Therefore, ina region having such a potential gradient as described above, the liquidcrystal molecules 30 a are inclined in the direction of the potentialgradient.

As the area (length in a cross-sectional view) of the second region R2increases, there may be a region with no potential gradient in thevicinity of the center of the second region R2. (this is indicated byvertical electric force lines EF in FIG. 1A). The liquid crystalmolecules 30 a in this region are not subject to a torque from anelectric field which would incline the liquid crystal molecules 30 a ina particular direction. However, the second region R2 is providedbetween the first region R1 and the third region R3, and the liquidcrystal molecules 30 a are inclined in the same direction according tothe direction of the produced potential gradient in the vicinity of theboundary between the first region R1 and the second region R2 and in thevicinity of the boundary between the second region R2 and the thirdregion R3. Therefore, the liquid crystal molecules present in thevicinity of the center of the second region R2 are influenced by thechange in the orientation of the liquid crystal molecules 30 a in thevicinity of the boundaries so as to be inclined in the same direction.In other words, the liquid crystal molecules 30 a in the vicinity of theboundary between the second region R2 and the first region R1 and thosein the vicinity of the boundary between the second region R2 and thethird region R3 (which influence the orientation direction (inclinationdirection) of the liquid crystal molecules 30 a present in the vicinityof the center of the second region R2 in which the inclination directionis not uniquely regulated by an electric field) are both inclined in thesame direction. As a result, all of the liquid crystal molecules 30 aare stably inclined in the same direction within eachorientation-regulating region T1 or T2.

The greater is the extent of the second region R2, the larger theportion (a portion of the second region) where a uniform orientation isexhibited in a picture element region. The region where a uniformorientation is exhibited is a region where a uniform transmittance isobtained in a produced liquid crystal display device. The larger is thisregion, the higher the transmittance of the entire picture elementregion can be made (ideally, a uniform orientation should be exhibitedacross the entire picture element region as in, for example, a TN typeliquid crystal display device known in the art), thereby providing anadvantage in terms of the light efficiency.

As is apparent from the above description, the potential of the lowerconductive layer 11 and the potential of the upper conductive layer 13can be set so that the voltage applied across the liquid crystal layer30 in the second region R2 is lower than the voltage applied across theliquid crystal layer 30 in the first region R1, thereby producing asufficient potential gradient to regulate the orientation direction(inclination direction) of the liquid crystal molecules 30 a in thevicinity of the boundary therebetween. The potential of the lowerconductive layer 11 and the potential of the upper conductive layer 13can be set in view of the voltage decrease due to the presence of thedielectric layer 12. If the degree of voltage drop by the dielectriclayer 12 is sufficiently high, the lower conductive layer 11 and theupper conductive layer 13 can have the same potential. In such a case,there is an advantage that the structure of the liquid crystal displaydevice 100 can be simplified. If the degree of voltage drop by thedielectric layer 12 is not sufficiently high, the potential of the lowerconductive layer 11 can be set to be lower than the potential of theupper conductive layer 13 so that a sufficient potential gradient can beobtained.

In the description above, the correlation between the potentials of thelower conductive layer 11 and the upper conductive layer 13 with respectto the potential of the second electrode 22 has been described.Generally, an orientation-regulating force from an electric field can beobtained if the relationship Vb≦Va<Vc or Vb≧Va>Vc is satisfied, whereinVa denotes the potential of the lower conductive layer 11, Vb denotesthe potential of the upper conductive layer 13, and Vc denotes thepotential of the second electrode 22. The specific level of potentialcan be suitably set so as to obtain a desirable response speed and adesirable viewing angle characteristic in view of the structure of theliquid crystal display device 100 (the size of each picture elementregion, the physical property of the liquid crystal material, the widthand number of openings, etc.).

In order to further clarify the characteristic function of the electrodestructure of the liquid crystal display device 100 according to thepresent invention, it will be compared with the function of aconventional electrode structure having an opening (slit).Conventionally, an opening is provided in an electrode made of a singleconductive film. The conventional electrode structure as ComparativeExample includes a first electrode 51 having an opening 51 a therein asillustrated in FIG. 2A and FIG. 2B. FIG. 2A and FIG. 2B correspond toFIG. 1A and FIG. 1D, respectively.

A liquid crystal display device 200 of Comparative Example illustratedin FIG. 2A and FIG. 2B can be considered as the liquid crystal displaydevice 100 from which the dielectric layer 12 and the upper conductivelayer 13 (and of course the upper layer opening 13 a) are removed. Itcan be considered that the lower conductive layer 11 and the lower layeropening 11 a correspond to the first electrode 51 and the opening 51 a,respectively. The other elements of the liquid crystal display device200 are denoted by the same reference numerals as those of the liquidcrystal display device 100, and will not be further described below.

In the presence of an applied voltage, an electric field as representedby electric force lines EF and an equipotential line EQ illustrated inFIG. 2A is produced in the liquid crystal layer 30 of the liquid crystaldisplay device 200. An inclined electric field (potential gradient) isproduced in the vicinity of the opening 51 a, and the liquid crystalmolecules 30 a are inclined in the direction of the inclined electricfield (potential gradient) (see FIG. 2A).

However, the electric force line EF of the electric field produced inthe vicinity of the center of the first electrode 51 is vertical to thesubstrate and has no potential gradient. Therefore, a torque which woulduniquely define the inclination direction does not act upon the liquidcrystal molecules 30 a present in the vicinity of the center of thefirst electrode 51, as indicated by a double-headed arrow in FIG. 2A.Moreover, the liquid crystal molecules 30 a in the vicinity of theopenings 51 a on opposing sides of the liquid crystal molecules 30 a inthe vicinity of the center of the first electrode 51 have oppositeinclination directions, and therefore the orientation direction of theliquid crystal molecules 30 a in the vicinity of the center of the firstelectrode 51 is not regulated by the orientations of those liquidcrystal molecules 30 a. Thus, there is no factor which uniquelyregulates the inclination direction of the liquid crystal molecules 30 ain the vicinity of the center of the first electrode 51 of the liquidcrystal display device 200. Therefore, the inclination direction ofthese liquid crystal molecules 30 a is dominated by very subtle anduncertain factors such as by chance (probability), subtle geometricvariations in the surface of the alignment layer (not shown), subtlevariations in the tilt angle, and subtle variations in the resistivityof the electrode 51.

Prior art also shows (e.g., Japanese Laid-Open Patent Publication No.11-109393) a structure similar to that illustrated in FIG. 2A and FIG.2B but with an additional electrode being provided on the lower side(away from the liquid crystal layer) of the opening 51 a via adielectric layer so as to cover the entirety of the opening 51 a with aconductive layer for the purpose of actively controlling the shape ofthe potential gradient, etc. Still, the behavior of the liquid crystalmolecules as described above, i.e., the uncertainty and instability ofthe inclination direction (rotation direction) of the liquid crystalmolecules in the vicinity of the center of the electrode 51 are notimproved.

As described above, with the conventional electrode structure of theliquid crystal display device 200, it is not possible to obtain anorientation-regulating force on the liquid crystal molecules located inthe vicinity of the center of the electrode 51. As a result, theboundary between the regions of different inclination directions (theadjacent regions whose inclination directions are respectively definedby the openings 51 a) is not well defined, whereby it is not possible torealize a desirable viewing angle characteristic.

In contrast, with the electrode structure of the liquid crystal displaydevice 100 of the present invention, the liquid crystal molecules 30 awhich are present on opposing sides of the liquid crystal molecules 30 aof the second region R2 which are not subject to a torque from anelectric field which would uniquely regulate the inclination direction(strictly speaking, they may be subject to an inclined electric field),i.e., the liquid crystal molecules 30 a which are present in thevicinity of the boundary between the second region R2 and the firstregion R1 and in the vicinity of the boundary between the second regionR2 and the third region R3, are inclined in the same direction by aninfluence of the inclined electric field. Therefore, with the change inthe orientation of these liquid crystal molecules 30 a being a trigger,the liquid crystal molecules 30 a of the second region R2 are alsouniquely inclined in the same direction as the liquid crystal molecules30 a on opposing sides thereof. Therefore, the electrode structure ofthe liquid crystal display device 100 according to the present inventiongenerates an orientation-regulating force which uniquely determines theinclination direction of the liquid crystal molecules 30 a across theentirety of the orientation-regulating region T1 or T2.

Next, a preferred arrangement of the orientation-regulating region T1 orT2 will be described.

Preferably, each of the upper layer opening 13 a and the lower layeropening 11 a has a side perpendicular to the direction in which theliquid crystal molecules 30 a are inclined, and the boundary between thefirst region R1 and the second region R2 and the boundary between thesecond region R2 and the third region R3 extend along the side of theupper layer opening 13 a and the lower layer opening 11 a, asillustrated in FIG. 1D. With such a structure, the directions of theinclined electric fields produced around the respective regionboundaries (between R1 and R2 and between R2 and R3) coincide with eachother also in terms of the azimuth angle direction, thereby increasingthe orientation-regulating effect. For example, each of the upper layeropening 13 a and the lower layer opening 11 a has a rectangular shapesuch that a pair of opposing sides thereof are perpendicular to theinclination direction.

For improving the viewing angle characteristic and the response speed,it is preferred to provide in each picture element region a plurality oforientation-regulating regions which regulate the orientation directionof the liquid crystal molecules in directions different from oneanother, thereby forming a multi-domain orientation. A sufficientresponse speed and viewing angle characteristic may be obtained evenwhen a mono-domain structure is employed for each picture elementregion. Since the display signals of adjacent picture element regionsare correlated with each other, it is possible to improve the viewingangle characteristic when the orientation directions of theorientation-regulating regions are different from each other betweenadjacent picture element regions. If a picture element region is small,it is possible to achieve a sufficient response speed by providing oneorientation-regulating region therein. Moreover, it is possible toimprove the response speed of a mono-domain-orientation picture elementregion by forming a plurality of orientation-regulating regions thereinwhich orient the liquid crystal molecules in the same direction.

It is possible to improve the viewing angle characteristic by the unitof picture element region by providing a plurality oforientation-regulating regions T1 or T2 for each picture element region.It is preferred to provide in each picture element regionorientation-regulating regions T1 (direction L) and T2 (direction −L)which define opposite inclination directions of the liquid crystaldisplay device 100. The orientation-regulating regions T1 and T2provided in each picture element region may take any of variousarrangements. For example, as illustrated in FIG. 1A and FIG. 1B, theorientation-regulating regions T1 having the arrangement direction L andthe orientation-regulating regions T2 having the arrangement direction−L may be provided in an alternating pattern so that the first region R1and the third region R3 are shared by the orientation-regulating regionT1 and the orientation-regulating region T2 which are adjacent to eachother. Alternatively, each picture element region may be provided with aregion TT3 in which the orientation-regulating regions T1 and T2adjacent to each other share the first region R1, or each pictureelement region may be provided with a region TT4 in which theorientation-regulating regions T1 and T2 adjacent to each other sharethe third region R3. Such arrangements can be easily realized byemploying the illustrated electrode structure.

Moreover, in order to obtain a highly symmetrical viewing anglecharacteristic, it is preferred to provide four or moreorientation-regulating regions having different inclination directions(orientation axes). Particularly, in order to obtain a liquid crystaldisplay device having a high light efficiency in addition to the highlysymmetrical viewing angle characteristic, it is preferred to providefour orientation-regulating regions respectively having four differentinclination directions. In such a case, it is preferred that the fourinclination directions (orientation axes) are such that any twoinclination directions selected from among the four inclinationdirections have an angle which is an integral multiple of about 90° withrespect to each other. Moreover, when the plurality oforientation-regulating regions provided for each picture element regioninclude a plurality of orientation-regulating regions having the sameinclination direction, it is preferred that the total area of theorientation-regulating regions of the same inclination direction isequal to that of other orientation-regulating regions of anotherinclination direction. It is preferred that there are four respectivelydifferent inclination directions, and it is more preferred that any twoinclination directions thereof have an angle which is an integralmultiple of about 90° with respect to each other. Moreover, it ispreferred that the number of orientation-regulating regions having oneof the four inclination directions is equal to the number oforientation-regulating regions having any other one of the fourinclination directions, and it is more preferred that the area of eachorientation-regulating region is equal to that of any otherorientation-regulating region.

As described above, it is preferred to provide in each picture elementregion a plurality of the orientation-regulating regions of the presentinvention. When a plurality of orientation-regulating regions areprovided, the number thereof, the positional relationship therebetween(e.g., the setting of the orientation axis direction), and the area (therespective areas of the orientation-regulating regions) can be suitablyset in view of the size and shape of the picture element region, therequired response speed and viewing angle characteristic.

A sufficient response speed and viewing angle characteristic may beobtained even when a mono-domain structure (a single inclinationdirection) is employed for each picture element region. Since thedisplay signals of adjacent picture element regions are correlated witheach other, it is possible to improve the viewing angle characteristicwhen the inclination directions of the orientation-regulating regionsare different from each other (preferably perpendicular to each other)between adjacent picture element regions. In the case of a color displaydevice, this can be achieved by employing different inclinationdirections for adjacent pixel regions, each pixel region being comprisedof R, G and B picture element regions. If a picture element region issmall, it is possible to achieve a sufficient response speed byproviding one orientation-regulating region therein. Moreover, it ispossible to improve the response speed of a mono-domain-orientationpicture element region by forming a plurality of orientation-regulatingregions therein which have the same inclination direction.

As described above, the second electrode 22 opposing the first electrode14 is not required to have any special structure for obtaining theeffects of the present invention, and may be one which has a knownelectrode structure. Therefore, the following combinations, for example,are possible as the combination of the first electrode and the secondelectrode. TABLE 1 First electrode Second electrode Active matrix typePicture element Counter electrode electrode (common electrode) Counterelectrode Picture element (common electrode) electrode Japanese PatentCounter striped Picture element Publication for electrode electrodeOpposition No. Picture element Counter striped 7-113722 (see FIG. 7)electrode electrode PALC (see FIG. 9) Striped electrode Virtualelectrode (thin dielectric plate)

Moreover, with an active matrix type liquid crystal display device or aliquid crystal display device disclosed in Japanese Patent Publicationfor Opposition No. 7-113722, the second electrode 22 may have a similarstructure to that of the first electrode 14 for each of thecombinations.

Preferred embodiments of the present invention will now be described.

EMBODIMENT 1

A liquid crystal display device of Embodiment 1 is an active matrix typeliquid crystal display device using TFTs, wherein picture elementelectrodes arranged in a matrix having rows and columns function as thefirst electrode, and a counter electrode which is used commonly to theplurality of picture element electrodes functions as the secondelectrode.

FIG. 3A and FIG. 3B schematically illustrate a liquid crystal displaydevice 300 according to Embodiment 1 of the present invention. FIG. 3Ais a plan view schematically illustrating a single picture elementregion (a TFT element, a storage capacitor element, etc., are omitted),and FIG. 3B is a cross-sectional view taken along line 3B-3B′ of FIG.3A.

The liquid crystal display device 300 includes a TFT substrate 300 a, acounter substrate 300 b and a liquid crystal layer 330 provided betweenthe TFT substrate 300 a and the counter substrate 300 b. The liquidcrystal layer 330 is a vertical alignment type liquid crystal layercontaining liquid crystal molecules (not shown) having a negativedielectric anisotropy. Vertical alignment films 315 and 325 are providedon one surface of the TFT substrate 300 a and the counter substrate 300b, respectively, which is closer to the liquid crystal layer 330.

The TFT substrate 300 a of the liquid crystal display device 300includes a glass substrate 310 and a picture element electrode 314provided on the surface thereof. The counter substrate 300 b includes acolor filter substrate 320 and a counter electrode 322 provided on thesurface thereof. The orientation of the liquid crystal layer 330 foreach picture element region changes according to the voltage appliedbetween the picture element electrode 314 and the counter electrode 322which are arranged so as to oppose each other via the liquid crystallayer 330 therebetween.

The picture element electrode 314 of the liquid crystal display device300 includes a lower conductive layer 311, a dielectric layer 312covering the lower conductive layer 311, and an upper conductive layer313 provided on one side of the dielectric layer 312 which is closer tothe liquid crystal layer 330. The lower conductive layer 311 includes alower layer opening 311 a, and the upper conductive layer 313 includesan upper layer opening 313 a. The lower layer opening 311 a is arrangedso as to be located within the upper layer opening 313 a. The upperconductive layer 313 and the lower conductive layer 311 are electricallyconnected to each other via a contact hole 312 a provided in thedielectric layer 312, and thus are at the same potential. The lowerconductive layer 311 and the upper conductive layer 313 are electricallyconnected to a driving circuit (not shown) via a TFT (not shown). TheTFT and the driving circuit may have structures known in the art.

The two-dimensional structure of the picture element electrode 314 willbe described with reference to FIG. 3A. The shape of the picture elementelectrode 314 is an elongated rectangular shape as illustrated in FIG.3A. The upper conductive layer 313 and the lower conductive layer 311are each formed of a continuous conductive film. Each of the lower layeropening 311 a and the upper layer opening 313 a has a side extending ina direction at 45° with respect to the longer side and the shorter sideof the picture element electrode 314 (the column direction and the rowdirection of the matrix arrangement). The direction in which the sideextends differs by 90° between the upper half and the lower half of thepicture element electrode 314.

First, the upper half of the picture element region in FIG. 3A will befocused upon. As illustrated in FIG. 3B, the structure of the crosssection taken along line 3B-3B′ is substantially the same as thatillustrated in FIG. 1A. Therefore, as illustrated in FIG. 3A, the upperhalf of the picture element region of the liquid crystal display device300 includes two pairs of orientation-regulating regions T1 and T2having opposite liquid crystal molecule inclination directions, and theliquid crystal molecules in the orientation-regulating regions T1 and T2are inclined as indicated by arrows in the figure. The lower half of thepicture element region in FIG. 3A is in axisymmetry with the upper halfwith respect to the shorter side direction (e.g., the row direction) ofthe picture element electrode 314. The orientation-regulating regions T3and T4 of the lower half have substantially the same function as that ofthe orientation-regulating regions T1 and T2 of the upper half exceptthat the liquid crystal molecule inclination direction is different by90°.

As described above, the picture element region of the liquid crystaldisplay device 300 includes the orientation-regulating regions T1, T2,T3 and T4 having different liquid crystal molecule inclinationdirections (sometimes referred to as a “4-division multi-domainorientation”), thereby providing a desirable viewing anglecharacteristic. The orientation-regulating regions T1, T2, T3 and T4have an equal area. Moreover, the four orientation-regulating regionsT1, T2, T3 and T4 incline the liquid crystal molecules in respectivedirections (azimuth angle directions) which are shifted from one anotherby 90°. Thus, the uniformity of the viewing angle characteristic ishigh. In the illustrated example, two of each of theorientation-regulating regions T1, T2, T3 and T4 (a total of 8orientation-regulating regions) are provided. However, it is notnecessary to provide so many orientation-regulating regions. Generally,in view of the viewing angle characteristic, a sufficient characteristiccan be obtained by dividing each picture element region into fourorientation-regulating regions of different orientation directions. Thenumber of orientation-regulating regions for each picture element regioncan be selected according to the required response speed.

The thickness d_(LC) of the liquid crystal layer 330 (referred to alsoas the “cell gap”) of the liquid crystal display device 300 is, forexample, about 4 μm. As the liquid crystal material, a typical liquidcrystal material having a negative dielectric anisotropy (for example,MJ95955 manufactured by Merck & Co., Inc.: dielectric constants ε

=3.4, ε_(⊥)=6.7, Δε=−3.3) is used. As the vertical alignment films 315and 325, a typical vertical alignment film (for example, JALS2004manufactured by JSR) is used. The thickness d_(LC) of the liquid crystallayer 330 is not limited to the example above, but may take any othervalue as long as it is generally in the range of about 2 μm to about 20μm and the product between the refractive index anisotropy Δn of theliquid crystal material and d_(LC) (“retardation”) is in the range of100 nm to 500 nm.

The thickness d_(D) of the dielectric layer 312 is, for example, about 3μm. The dielectric layer 312 is formed by using a typical organicmaterial (for example, a photosensitive organic insulative materialhaving a relative dielectric constant of about 3.4). The material of thedielectric layer 312 is not limited to an organic material (typically, apolymer material), but may alternatively be an inorganic material (forexample, silicon oxide (SiO_(x)) or silicon nitride (SiN_(x))).

The thickness d_(D) of the dielectric layer 312 is not limited to theexample above, but may take any other value as long as it is about 0.01to about 1000 times the thickness d_(LC) of the liquid crystal layer330. The thickness d_(D) of the dielectric layer 312 is preferably inthe range of 0.5 to 5 μm, and more preferably in the range of 1 to 3 μm.Alternatively, the thickness d_(D) of the dielectric layer 312 ispreferably such that the value ε_(D)/d_(D) is about 0.05 to about 20,and more preferably about 0.3 to 5, times the value ε

/d_(LC) (wherein ε_(D) denotes the dielectric constant of the dielectriclayer 312, d_(LC) the thickness of the liquid crystal layer 330, and ε

the dielectric constant of the liquid crystal material).

When the thickness d_(D) of the dielectric layer 312 increases, thevoltage applied across the liquid crystal layer 330 above the upperlayer opening 313 a decreases due to the capacitance division of thedielectric layer 312 and the liquid crystal layer 330, thereby requiringa high voltage in order to obtain a desirable transmittance. On theother hand, when the voltage decrease by the dielectric layer 312increases, the inclination (bending) of an electric field produced inthe vicinity of the boundary of the upper layer opening 313 a increases,thereby providing an advantageous effect that the orientation-regulatingforce increases. The thickness d_(D) of the dielectric layer 312 can besuitably set as necessary.

The width W of the upper conductive layer 313 illustrated in FIG. 3B(corresponding to the width of R1 in FIG. 1A) and the width S of thelower layer opening 311 a (corresponding to the width of R3 in FIG. 1A)are each 10 μm, for example. The width W and the width S are each awidth in a direction perpendicular to the direction in which the liquidcrystal molecules are inclined in the orientation-regulating region. Thewidths W and S are not limited to the value shown above, but may takeany other value as long as it is about 0.1 to about 100 times thethickness d_(LC) of the liquid crystal layer 330. The preferred rangefor the widths W and S depends upon the thickness d_(LC) of the liquidcrystal layer 330 because the electric field distribution produced inthe liquid crystal layer 330 is dependent upon the physical positions ofthe lower conductive layer 311, the upper conductive layer 313 and thecounter electrode 322 (the inter-electrode distance) and the dielectricconstant of the dielectric layer 312 and the liquid crystal layer 330being interposed therebetween. In view of the dielectric constants oftypical dielectric materials and liquid crystal materials, a sufficientorientation-regulating force can be realized by setting the widths W andS generally in the above-described range.

The pitch P of the upper conductive layer 313 (corresponding to thewidth of (R2×2)+R1+R3 in FIG. 1A) is 50 μm, for example. Therefore, thewidth of the upper layer opening 313 a in the illustrated structure ispitch P (50 μm)−width W of the upper conductive layer (10 μm), thus 40μm. In this way, the structure of the lower conductive layer 311, thelower layer opening 311 a, the upper conductive layer 313 and the upperlayer opening 313 a can be optimized.

Generally, each of the width of the first region (corresponding to thewidth of R1 in FIG. 1A, or the width W in FIG. 3B) and the width of thethird region (corresponding to the width of R3 in FIG. 1A, or the widthS in FIG. 3B) is preferably about 1 μm to about 100 μm. When the widthis less than 1 μm, the inclination of an electric field in the vicinityof the boundary between the first region and the second region and theboundary between the second region and the third region is reduced sothat a sufficient orientation-regulating force cannot be obtained. As aresult, the response speed may be too slow or the orientation stabilitymay be undesirably low. When the width is greater than 200 μm, asufficient orientation-regulating force may not be obtained for theliquid crystal molecules in the vicinity of the center of the region,thereby deteriorating the display quality. A more preferred range forthe width of the first and third regions is about 5 μm to about 20 μm,and the range of about 10 μm to about 20 μm is particularly preferred.When these widths are too small, a sufficient orientation-regulatingforce cannot be obtained, and the widths being too large are notpreferred because then the region which is not used for displayincreases.

The width of the second region (corresponding to the width of R2 in FIG.1A, or (P−W−S)/2 in FIG. 3B) is preferably about 5 μm to about 1000 μm.When the width is smaller than 5 μm, an electric field is inclined inall of the first, second and third regions, whereby the rotation angle(inclination angle) of the liquid crystal molecules, i.e., theretardation value of the liquid crystal layer, varies throughout theregions. As a result, the light efficiency decreases. When the width ofthe second region is greater than 1000 μm, the light efficiencyincreases, but the response speed decreases significantly. The reasonfor this is as follows. When the width of the second region is so large,the electric field in the central portion of the second region in thewidth direction thereof is not inclined, whereby anorientation-regulating force from the electric field is not generated.The liquid crystal molecules in the central portion are inclined in acertain direction by being influenced by the orientation of the liquidcrystal molecules which are inclined in the vicinity of the boundarybetween the second region and the first region and in the vicinity ofthe boundary between the second region and the third region. Therefore,as the distance from the central portion of the second region to itsboundary with the adjacent first or third region increases, thepropagation of the influence from the orientation of the liquid crystalmolecules in the vicinity of the boundary slows down or is lost. Inorder to obtain a sufficient orientation-regulating force and lightefficiency, the width of the second region is more preferably in therange of about 10 μm to about 50 μm.

Thus, the electrode structure for producing a sufficientorientation-regulating force of the present invention can be obtained bysuitably setting the number of regions into which a picture elementregion is divided (the variation in the number of orientation-regulatingregions and the inclination direction thereof), the width W of the upperconductive layer 313, the width S of the lower layer opening 311 a, thepitch P of the upper conductive layer 313, etc., according to the sizeand shape of a picture element region of the particular liquid crystaldisplay device to be produced. The variation in the division number andthe inclination direction is set primarily in connection with theviewing angle characteristic, and the physical structure (size, shape,etc.) of the electrode is set primarily in connection with the responsespeed.

The lower conductive layer 311 and the upper conductive layer 313 of thepicture element electrode 314, and the counter electrode 322, are formedby using a transparent conductive material (ITO), for example. The upperconductive layer 313 may be formed by using an opaque material becauseit has a high proportion of the upper layer opening 313 a. The upperconductive layer 313 may be formed by using a metal material (e.g.,aluminum, an aluminum alloy, copper). The metal material is generallysuperior to a transparent conductive material in terms of themachinability, and therefore preferably used as a material of the upperconductive layer 313, in which case a minute pattern can be formedefficiently.

The liquid crystal display device 300 having such a structure asdescribed above can function as a transmission type liquid crystaldisplay device. However, the liquid crystal display device 300 can beprovided as a reflection type liquid crystal display device by, forexample, forming the upper conductive layer 313 and the lower conductivelayer 311 by using a metal material.

The liquid crystal display device 300 having such a structure asdescribed above is provided with, for example, polarizers (including apolarizing plate, a polarizing film, and the like) 404 and 405, phasedifference compensation elements (including a phase plate, a phase film,and the like) 402 and 403, and a backlight 406, as illustrated in FIG.4, thereby obtaining a transmission type liquid crystal display device400 of a normally black mode having a desirable display quality. In FIG.4, arrows in the polarizers 404 and 405 denote the respectivetransmission axes (polarization axes) thereof, and arrows in the phasedifference compensation elements 402 and 403 denote the primary axisdirections of index ellipsoids representing the respective refractiveindex anisotropies of the phase difference compensation elements.

The polarizers 404 and 405 are arranged in a crossed-Nicols state so asto produce a black display in the absence of an applied voltage (whenthe liquid crystal layer 330 is in a vertical alignment). Thetransmission axes of the polarizers 404 and 405 are arranged in parallelto the top-bottom direction and the left-right direction, respectively,of the display plane. The transmission axes are typically arranged so asto form an angle of 45° with respect to the inclination directions ofthe orientation-regulating regions T1, T2, T3 and T4 which are indicatedby arrows in FIG. 3A. It is possible to improve the transmittance (thelight efficiency) by dividing each picture element region into fourregions so that the inclination direction of each of theorientation-regulating regions T1, T2, T3 and T4 forms an angle of 45°with respect to the transmission axis of each of the polarizers 404 and405 which are arranged in a crossed-Nicols state.

The phase difference compensation elements 402 and 403 are designed soas to compensate for changes in the retardation value of the liquidcrystal layer 330 due to changes in the viewing angle in a black displaystate in the absence of an applied voltage. This design can be achievedby using a method known in the art.

FIG. 5 illustrates the applied voltage dependency of the transmittanceof the liquid crystal display device 400. As is apparent from FIG. 5,the liquid crystal display device 400 has a desirablevoltage-transmittance characteristic of a normally black mode. Thevertical axis of FIG. 5 denotes the relative transmittance, and thehorizontal axis denotes the absolute value of the voltage appliedbetween the picture element electrode 314 and the counter electrode 322.

Next, FIG. 6 illustrates an iso-contrast contour curve (contrastratio=30) of the liquid crystal display device 400. The symbol ψ in theiso-contrast contour curve denotes the azimuth angle (the angle in thedisplay plane), with ψ=0° corresponding to the 12 o'clock direction ofthe display plane, and the value increasing as the angle movesclockwise. The symbol θ denotes the viewing angle (the angle withrespect to the normal to the display plane), and the value increases asthe viewing angle moves radially away from the center of the circle. Asis apparent from FIG. 6, the contrast ratio is 30 or more in the regionwhere the viewing angle θ is 60° or less for substantially any azimuthangle ψ, thus indicating that the liquid crystal display device 400 hasa desirable viewing angle characteristic. Moreover, as illustrated inFIG. 6, the azimuth angle dependency of the viewing angle characteristicis uniform (i.e., the contour pattern is equivalent for any of the fourdirections; the contour pattern has a four-fold rotational symmetry).Thus, it is assumed that the liquid crystal display device 400 has adesirable 4-division multi-domain orientation. In the liquid crystaldisplay device 400, whether or not a desirable 4-division multi-domainorientation is realized for each picture element region according to theorientation-regulating forces produced respectively in theorientation-regulating regions T1, T2, T3 and T4 illustrated in FIG. 3Acan be confirmed by observing with a microscope the picture elementregion from an inclined direction (with respect to the normal to thedisplay plane).

While a typical TFT type liquid crystal display device has been shownabove as an example of the liquid crystal display device 300, thepresent invention can be used with a TFT type liquid crystal displaydevice having a structure as illustrated in FIG. 7 which is disclosedin, for example, Japanese Patent Publication for Opposition No.7-113722.

A liquid crystal display device 500 illustrated in FIG. 7 includes afirst substrate 500 a, picture element electrodes 514 arranged in amatrix, TFTs 516 whose drains are connected to the picture elementelectrodes 514, and scanning lines (scanning bus lines) 517 which areconnected to the gates of the TFTs 516. A second substrate 500 b whichopposes the first substrate 500 a via the liquid crystal layer (notshown) therebetween includes signal lines (data bus lines) 522 arrangedin a stripe pattern on the side of the liquid crystal layer. Thescanning lines 517 and the signal lines 522 extend perpendicular to eachother. The TFT type liquid crystal display device 500 is different fromthe above-described typical TFT type liquid crystal display device whichhas a single counter electrode used commonly to all of the pictureelement electrodes in that the former includes, as the electrodes on thesecond substrate 500 b, signal lines electrically independent of eachother and arranged in a stripe pattern. Also in the liquid crystaldisplay device 700, the effects of the present invention can be obtainedby employing the structure of the picture element electrode 314illustrated in FIG. 3A and FIG. 3B for the picture element electrode514.

EMBODIMENT 2

The TFT type liquid crystal display device 300 of Embodiment 1 employsthe structure of the first electrode 14 illustrated in FIG. 1A for thepicture element electrodes of the conventional TFT type liquid crystaldisplay device. In contrast, a TFT type liquid crystal display device ofEmbodiment 2 employs a structure similar to that of the first electrode14 illustrated in FIG. 1A for a counter electrode of the conventionalTFT type liquid crystal display device. The structure of the liquidcrystal display device of Embodiment 2 may be the same as that of theconventional liquid crystal display device (having the structure of theliquid crystal display device 300 of Embodiment 1 except for the pictureelement electrode 314) except for the structure of the counterelectrode. Accordingly, only the structure of the counter electrode willbe described below.

FIG. 8 shows a plan view of a counter substrate 600 b of the liquidcrystal display device of Embodiment 2. The counter substrate 600 bincludes a counter electrode 614 on one side thereof which is closer tothe liquid crystal layer. The counter electrode 614 includes a lowerconductive layer 611, a dielectric layer 612 covering the lowerconductive layer 611, and an upper conductive layer 613 provided on oneside of the dielectric layer 612 which is closer to the liquid crystallayer. The lower conductive layer 611 includes a lower layer opening 611a, and the upper conductive layer 613 includes an upper layer opening613 a. The lower layer opening 611 a is arranged so as to be locatedwithin the upper layer opening 613 a. The upper conductive layer 613 andthe lower conductive layer 611 are electrically connected to each otheralong their straight portions 611S and 613S extending in the columndirection of the matrix, for example, and thus are at the samepotential. The dielectric layer 612 along the straight portions 611S and613S includes contact holes (not shown; not limited to holes, but may begrooves) for electrically connecting the upper conductive layer 613 andthe lower conductive layer 611 to each other.

The counter electrode 614 has a structure similar to that of the firstelectrode 14 illustrated in FIG. 1A, corresponding to, for example, anelongated rectangular picture element electrode (not shown; for example,70 μm×210 μm for 18-inch type SXGA). For example, two rectangularregions in FIG. 8 (those provided with arrows therein) correspond to asingle rectangular picture element region. The respective widths L1 andS1 of the upper conductive layer 613 and the lower layer opening 611 awhich are each arranged in a striped pattern between two adjacent upperlayer openings 613 a are set similarly to the widths W and S,respectively, of the liquid crystal display device 300 of Embodiment 1.Each of the lower layer opening 611 a and the upper layer opening 613 ahas a side extending in a direction at 45° with respect to the longerside and the shorter side of the picture element region (the columndirection and the row direction of the matrix arrangement). Thedirection in which the side extends differs by 90° between the upperhalf and the lower half of the picture element region. This structure ofthe regions corresponding to a single picture element region of thecounter electrode 614 is similar to that of the picture elementelectrode 314 illustrated in FIG. 3A, forming the orientation-regulatingregions T1, T2, T3 and T4.

Thus, the picture element region of the liquid crystal display device ofthe present embodiment includes the orientation-regulating regions T1,T2, T3 and T4 having different liquid crystal molecule inclinationdirections (sometimes referred to as a “4-division multi-domainorientation”), thereby providing a desirable viewing anglecharacteristic as the liquid crystal display device of Embodiment 1. Inthe liquid crystal display device of the present embodiment, whether ornot a desirable 4-division multi-domain orientation is realized for eachpicture element region according to the orientation-regulating forcesproduced respectively in the orientation-regulating regions T1, T2, T3and T4 illustrated in FIG. 8 can be confirmed by observing with amicroscope the picture element region from an inclined direction (withrespect to the normal to the display plane).

In order to prevent the orientation of the liquid crystal molecules frombeing disturbed by an external electric field (an electric field causedby a electrostatic charge, etc.) entering the liquid crystal layerthrough the lower layer opening 611 a, it is preferred that a conductivelayer fixed to a certain potential is provided surrounding the lowerlayer opening 611 a (for example, surrounding the counter substrate, thesurface of a polarizer, or under a further dielectric layer providedunder (on the substrate side of) the lower layer opening 611 a).

Moreover, the liquid crystal display device is provided with thepolarizers (including a polarizing plate, a polarizing film, and thelike) 404 and 405, the phase difference compensation elements (includinga phase plate, a phase film, and the like) 402 and 403, and thebacklight 406, as illustrated in FIG. 4, thereby obtaining atransmission type liquid crystal display device of a normally black modehaving a desirable display quality.

EMBODIMENT 3

According to the present invention, it is possible to obtain asufficient orientation-regulating force by, for example, employing anelectrode structure similar to that of the first electrode 14illustrated in FIG. 1A for the structure of one of a pair of electrodeswhich oppose each other via a liquid crystal layer therebetween.Therefore, even with a PALC, for which it is difficult to obtain anorientation-regulating force with the conventional structure (e.g., thatdisclosed in Japanese Laid-Open Patent Publication No. 11-258606), asufficient orientation-regulating force can be obtained by employing theelectrode structure of the present invention.

The structure and operation of a liquid crystal display device 700 ofEmbodiment 3, which uses the present invention with a PALC, will now bedescribed.

FIG. 9 schematically illustrates the liquid crystal display device 700of Embodiment 3. The liquid crystal display device 700 includes a liquidcrystal display cell 701 and a plasma cell 702. The liquid crystaldisplay cell 701 and the plasma cell 702 share a thin dielectric plate703.

The liquid crystal display cell 701 includes an upper substrate (e.g., aglass substrate) 704, a thin dielectric plate 703, and a liquid crystallayer 707 provided therebetween. A plurality of data electrodes 714arranged in a stripe pattern which extend in parallel to one other (in,for example, the row direction) are provided on one side of the uppersubstrate 704 which is closer to the liquid crystal layer 707. The uppersubstrate 704 and the thin dielectric plate 703 are attached to eachother while keeping a predetermined gap (cell gap) by means of a sealant706. The gap between the upper substrate 704 and the thin dielectricplate 703 is filled with a liquid crystal material having a negativedielectric anisotropy, and a vertical alignment film (not shown) isprovided on one surface of each of the upper substrate 704 and the thindielectric plate 703 which is closer to the liquid crystal layer 707.The liquid crystal layer 707 is in a vertical alignment in the absenceof an applied voltage.

The plasma cell 702 includes a plurality of plasma discharge channels712 extending in parallel to one another (in, for example, the columndirection) which are formed by a lower substrate (for example, a glasssubstrate) 708, the thin dielectric plate 703, and partition walls 710provided therebetween. On one side of the lower substrate 708 which iscloser to the plasma discharge channels 712, a plurality of anodeelectrodes 709 a and a plurality of cathode electrodes 709 b extendingin parallel to each other (in, for example, the column direction) areprovided in an alternating pattern with a predetermined intervaltherebetween. The anode electrodes 709 a and the cathode electrodes 709b are sometimes referred to collectively as a “plasma electrode 709”.The partition walls 710 are provided with a predetermined width so as toextend in parallel to one another and substantially along the centralportion of the upper surface of each of the anode electrodes 709 a andthe cathode electrodes 709 b. The lower substrate 708 along theperiphery thereof is hermetically attached to the thin dielectric plate703 by means of a frit seal 715 using a low melting point glass, or thelike. The plasma discharge channels 712 are filled with an ionizable gas(for example, helium, neon, argon, or a mixed gas thereof), and a plasmadischarge occurs by applying a voltage through the gas by the plasmaelectrode 709.

The plasma discharge channels 712 and the data electrodes 714 areperpendicular to each other. Each of the data electrodes 714 is a unitof column driving operation, for example, and each of the plasmadischarge channels 712 is a unit of row driving operation, for example.Each intersection between the data electrodes 714 and the plasmadischarge channels 712 defines a picture element region.

The liquid crystal display device 700 operates as follows.

When a predetermined voltage is applied between the anode electrode 709a and the cathode electrode 709 b which correspond to a predeterminedplasma discharge channel 712, the gas in the plasma discharge channel712 is selectively ionized to generate a plasma discharge, and theinside of the plasma discharge channel 712 is kept generally at theanode potential (row addressing state; write period). In this state, ifa data voltage is applied to the data electrode 714, a voltagecorresponding to the difference between the anode potential and the datapotential of the data electrode 714 is applied via the thin dielectricplate 703 across the liquid crystal layer 707 of the picture elementregions which are arranged in the column direction corresponding to theplasma discharge channel 712. At this time, a region of the thindielectric plate 703 corresponding to the plasma discharge channel 712which is in a discharge state functions as a virtual scanning electrode.Thus, data is written to the picture element regions arranged in thecolumn direction.

Upon completion of the plasma discharge, the inside of the plasmadischarge channel 712 has a floating potential, whereby the data voltagewhich has been written to the liquid crystal layer 707 of each pictureelement region is maintained until the following write period which is,for example, one field or one frame later. In such a case, the plasmadischarge channel 712 functions as a sampling switch while the liquidcrystal layer 707 of each picture element region functions as a samplingcapacitor.

An image is displayed by successively scanning, in the row direction,the plasma discharge channels 712 which extend in the column direction,thereby writing data voltages from the data electrodes 714 extending inthe row direction to the liquid crystal layer 707 of a plurality ofpicture element regions arranged in the column direction.

In the PALC, the voltage applied across the liquid crystal layer 707corresponds to a voltage which is obtained by dividing the potentialdifference between the anode potential and the data potential of thedata electrode 714 by the thin dielectric plate 703 and the liquidcrystal layer 707. Therefore, it is preferred to reduce the thickness ofthe thin dielectric plate 703 as much as possible in order to suppressas much as possible the voltage drop by the thin dielectric plate 703.Typically, a thin glass plate having a thickness of about 50 μm is used.Since such a thin glass plate is poor in physical strength, it is verydifficult to form a special structure on the thin dielectric plate 703.Therefore, it is not possible to use an orientation-regulating methodwhich requires a special structure to be provided on substrates on bothsides of the liquid crystal layer, as that disclosed in JapaneseLaid-Open Patent Publication No. 11-258606.

In the liquid crystal display device 700 of Embodiment 3, the dataelectrode 714 has a structure similar to that of the first electrode 14illustrated in FIG. 1A. FIG. 11 schematically illustrates the planarstructure of the data electrode 714 of the liquid crystal display device700.

The data electrode 714 includes a lower conductive layer 711, adielectric layer 712 covering the lower conductive layer 711, and anupper conductive layer 713 provided on one side of the dielectric layer712 which is closer to the liquid crystal layer. The lower conductivelayer 711 includes a lower layer opening 711 a, and the upper conductivelayer 713 includes an upper layer opening 713 a. The lower layer opening711 a is arranged so as to be located within the upper layer opening 713a. The upper conductive layer 713 and the lower conductive layer 711 areelectrically connected to each other along their straight portions 711Sand 713S extending in the column direction of the matrix, for example,and thus are at the same potential. The dielectric layer 712 along thestraight portions 711S and 713S includes contact holes (not shown; notlimited to holes, but may be grooves) for electrically connecting theupper conductive layer 713 and the lower conductive layer 711 to eachother.

The data electrode 714 has a structure similar to that of the firstelectrode 14 illustrated in FIG. 1A, corresponding to, for example, anelongated rectangular picture element electrode (not shown; for example,70 μm×210 μm for 18-inch type SXGA). For example, two rectangularregions in FIG. 11 (those provided with arrows therein) correspond to asingle rectangular picture element region. The respective widths L2 andS2 of the upper conductive layer 713 and the lower layer opening 711 awhich are each arranged in a striped pattern between two adjacent upperlayer openings 713 a are set similarly to the widths W and S,respectively, of the liquid crystal display device 300 of Embodiment 1.Each of the lower layer opening 711 a and the upper layer opening 713 ahas a side extending in a direction at 45° with respect to the longerside and the shorter side of the picture element region (the columndirection and the row direction of the matrix arrangement). Thedirection in which the side extends differs by 90° between the upperhalf and the lower half of the picture element region. This structure ofthe regions corresponding to a single picture element region of the dataelectrode 714 is similar to that of the picture element electrode 314illustrated in FIG. 3A, forming the orientation-regulating regions T1,T2, T3 and T4.

Thus, the picture element region of the liquid crystal display device ofthe present embodiment includes the orientation-regulating regions T1,T2, T3 and T4 having different liquid crystal molecule inclinationdirections (sometimes referred to as a “4-division multi-domainorientation”), thereby providing a desirable viewing anglecharacteristic as the liquid crystal display device of Embodiment 1. Inthe liquid crystal display device of the present embodiment, whether ornot a desirable 4-division multi-domain orientation is realized for eachpicture element region according to the orientation-regulating forcesproduced respectively in the orientation-regulating regions T1, T2, T3and T4 illustrated in FIG. 11 can be confirmed by observing with amicroscope the picture element region from an inclined direction (withrespect to the normal to the display plane).

Moreover, the liquid crystal display device is provided with thepolarizers (including a polarizing plate, a polarizing film, and thelike) 404 and 405, the phase difference compensation elements (includinga phase plate, a phase film, and the like) 402 and 403, and thebacklight 406, as illustrated in FIG. 4, thereby obtaining atransmission type liquid crystal display device of a normally black modehaving a desirable display quality.

In Embodiments 1 to 3 above, a case where a 4-division multi-domainorientation is realized by using the electrode structure of the presentinvention has been described, but the present invention is not limitedto such an example as described above.

For example, an axially symmetric orientation can be realized byemploying an electrode structure as illustrated in FIG. 12. A firstelectrode 814 illustrated in FIG. 12 can be used in place of the pictureelement electrode 314 illustrated in FIG. 3A, the counter electrode 614illustrated in FIG. 8, or the data electrode 714 illustrated in FIG. 11.

The first electrode 814 includes a lower conductive layer 811, adielectric layer 812 covering the lower conductive layer 811, and anupper conductive layer 813 provided on one side of the dielectric layer812 which is closer to the liquid crystal layer. The upper conductivelayer 813 provided corresponding to a rectangular picture element regionincludes three openings 813 a each having a generally square shape. Thelower conductive layer 811 includes lower layer openings 811 a each ofwhich has a shape similar to that of the upper layer opening 813 a andwhich are respectively located generally at the center of the upperlayer openings 813 a. The upper conductive layer 813 and the lowerconductive layer 811 are electrically connected to each other, forexample, under the upper conductive layer 813, and thus are at the samepotential. The dielectric layer 812 under the upper conductive layer 813includes contact holes (not shown; not limited to holes, but may begrooves) for electrically connecting the upper conductive layer 813 andthe lower conductive layer 811 to each other.

The cross-sectional structure of the first electrode 814 along, forexample, line 12A-12A′ is substantially the same as that of the regionTT4 of the first electrode 14 shown in FIG. 1A and FIG. 1B, and theupper layer openings 813 a and the lower layer openings 811 a all havesubstantially the same cross-sectional structure along a line whichincludes the center SA thereof. Therefore, the first electrode 814 hasan orientation-regulating force which inclines the liquid crystalmolecules in an axially symmetrical orientation with respect to thecenter SA.

The shape of the lower layer opening 811 a or the upper layer opening813 a is preferably close to a square so as to stabilize the axiallysymmetrical orientation, though it is not limited to a square. The sizeand arrangement of the lower layer openings 811 a and the upper layeropenings 813 a can be suitably set as in the preceding embodiments inview of the viewing angle characteristic and the responsecharacteristic. The two-dimensional arrangement of the openings in theelectrode structure of the present invention is not limited to any ofthose described above, but various modifications thereto can be made.

In order to stably obtain an axially symmetrical orientation, it ispreferred to mix an appropriate amount of chiral agent into a liquidcrystal material. The amount of chiral agent to be mixed in ispreferably such that the pitch of twist of the liquid crystal materialhaving the chiral agent mixed therein is about ½ to about 10 times thethickness of the liquid crystal layer. More preferably, the amount ofchiral agent to be mixed in is such that the twist angle of the liquidcrystal molecules is 80° to 100° when the maximum voltage to be used isapplied across the liquid crystal layer.

Moreover, in order to stably obtain an axially symmetrical orientation,the shape of the opening illustrated in FIG. 12 may be changed from asquare to a circle or a polygon. However, in order to effectively usethe picture element region, a square is most preferred. When a shapeother than a square is selected, a regular hexagon is preferred becauseregular hexagons can be closely arranged within a rectangular pictureelement. Although a regular polygon is preferred in view of symmetry, itis possible to realize a substantially axially symmetrical orientationeven if an irregular polygon is employed according to the shape of thepicture element region, etc.

Also in the present embodiment, a liquid crystal display device havingthe structure illustrated in FIG. 12 can be used in place of the liquidcrystal display device 300 of Embodiment 1 illustrated in FIG. 4. Insuch a case, the phase difference compensation elements 403 and 402 aresuitably designed by using a technique known in the art. As a result, itis possible to obtain a liquid crystal display device having a desirableviewing angle characteristic as in Embodiment 1.

Where an axially symmetrical orientation is employed as in the presentembodiment, it is preferred to employ, in the structure illustrated inFIG. 4, circular polarizers in place of the linear polarizers 404 and405. The reason for this is as follows. a phase difference compensationelement which most efficiently changes the polarization oflinearly-polarized light is a phase difference compensation elementwhich has a slow axis forming an angle of 45° with respect to thepolarization axis of the linearly-polarized light. Therefore, in aliquid crystal display device where a pair of linear polarizers arearranged in a crossed-Nicols state as illustrated in FIG. 12, thehighest light efficiency is obtained when the inclination direction ofthe liquid crystal molecules forms an angle which is an integralmultiple of 45° with respect to the polarization axis of the polarizers.In contrast, in an axially symmetrical orientation, the orientation axis(orientation direction) of the liquid crystal molecules continuouslychanges, whereby it is not possible to satisfy the positionalrelationship between the polarization axis of the linearly-polarizedlight and the orientation axis for all of the orientation axes. A phasedifference compensation element gives a change in the polarization in aconstant amount (the absolute value of the phase difference) forcircularly-polarized light irrespective of the angle of the slow axis.Therefore, in the present embodiment which employs a liquid crystallayer whose orientation axis continuously changes (which has an infinitenumber of slow axes), it is possible to obtain a liquid crystal displaydevice having a high light efficiency by substituting the linearpolarizers 404 and 405 with circular polarizers. In such a case, thephase difference compensation elements 402 and 403 can be suitablydesigned by using a technique known in the art.

As described above, according to the present invention, it is possibleto give an orientation-regulating force from an electric field to aliquid crystal layer containing vertically-aligned liquid crystalmolecules having a negative dielectric anisotropy. Therefore, accordingto the present invention, it is possible to obtain various types ofliquid crystal display devices having a desirable viewing anglecharacteristic.

According to the present invention, it is possible to obtain asufficient orientation-regulating force only by modifying the structureof one of a pair of electrodes for applying a voltage across a liquidcrystal layer. Thus, it is possible to provide a vertical alignment typeliquid crystal display device which has a sufficiently stableorientation and a sufficiently high response speed and yet can beproduced efficiently.

By variously changing the structure of an electrode which uses twoconductive layers each having openings, it is possible to realize aso-called multi-domain orientation (where there are a plurality ofregions of different liquid crystal molecule inclination directions) oran axially symmetrical orientation, and thus to improve the viewingangle characteristic. Moreover, it is possible to change the magnitudeof the orientation-regulating force by variously changing the electrodestructure, whereby it is possible to optimize the responsecharacteristic.

Moreover, the liquid crystal display device according to the presentinvention can be obtained only by changing the electrode structure in aconventional liquid crystal display device. Thus, the liquid crystaldisplay device according to the present invention can be produced byusing a conventional production method.

1-32. (Canceled)
 33. A liquid crystal display device, comprising: afirst substrate, a second substrate and a liquid crystal layerinterposed between the first substrate and the second substrate,wherein: a picture element region comprises a first electrode providedon one side of the first substrate which is closer to the liquid crystallayer and a second electrode provided on the second substrate so as tooppose the first electrode via the liquid crystal layer; the liquidcrystal layer is a vertical alignment type liquid crystal layercontaining a liquid crystal material having a negative dielectricanisotropy; and the picture element region includes at least oneorientation-regulating region, the orientation-regulating regionincluding a first region in which an electric field applied across theliquid crystal layer by the first electrode and the second electrode hasa first electric field strength, a second region in which the electricfield has a second electric field strength which is smaller than thefirst electric field strength, and a third region in which the electricfield has a third electric field strength which is smaller than thesecond electric field strength, wherein the first, second and thirdregions are arranged in this order in a predetermined direction; andwherein a boundary between the first region and the second region, and aboundary between the second region and the third region, are oriented soas to each extend in a direction perpendicular to the predetermineddirection.
 34. The liquid crystal display device of claim 33, wherein aplurality of the picture element regions are provided, and wherein eachof the plurality of picture element regions includes a plurality oforientation-regulating regions, the plurality of orientation-regulatingregions having the same direction of arrangement of the first, secondand third regions.
 35. The liquid crystal display device of claim 33,wherein a plurality of the picture element regions are provided, andwherein each of the plurality of picture element regions includes afirst orientation-regulating region in which the first, second and thirdregions are arranged in this order in a first direction, and a secondorientation-regulating region in which the first, second and thirdregions are arranged in this order in a second direction which isdifferent from the first direction.
 36. The liquid crystal displaydevice of claim 35, wherein each of the plurality of picture elementregions includes a plurality of at least one of the firstorientation-regulating region and the second orientation-regulatingregion.
 37. The liquid crystal display device of claim 35, wherein thefirst direction and the second direction are opposite to each other. 38.The liquid crystal display device of claim 37, each of the plurality ofpicture element regions further including a third orientation-regulatingregion in which the first, second and third regions are arranged in thisorder in a third direction which is different from the first and seconddirections, and a fourth orientation-regulating region in which thefirst, second and third regions are arranged in this order in a fourthdirection which is different from the first, second and thirddirections, wherein the third and fourth directions are perpendicular tothe first and second directions.
 39. The liquid crystal display deviceof claim 35, wherein the first orientation-regulating region and thesecond orientation-regulating region share at least one of the firstregion and the third region.
 40. A liquid crystal display device,comprising: a first substrate, a second substrate and a liquid crystallayer interposed between the first substrate and the second substrate,wherein: a plurality of picture element regions are provided, at leastone of the picture element regions being defined by at least a firstelectrode provided on one side of the first substrate which is closer tothe liquid crystal layer and a second electrode provided on the secondsubstrate so as to oppose the first electrode via the liquid crystallayer; the liquid crystal layer is a vertical alignment type liquidcrystal layer containing a liquid crystal material having a negativedielectric anisotropy; said picture element region includes at least oneorientation-regulating region, the orientation-regulating regionincluding a first region in which the first electrode and the secondelectrode have a first inter-electrode distance therebetween, a secondregion in which the first electrode and the second electrode have asecond inter-electrode distance therebetween which is greater than thefirst inter-electrode distance, and a third region in which the firstelectrode and the second electrode have a third inter-electrode distancetherebetween which is greater than the second inter-electrode distance,wherein the first, second and third regions are arranged in this orderin a predetermined direction; and wherein a boundary between the firstregion and the second region and a boundary between the second regionand the third region each extend in a direction perpendicular to thepredetermined direction.
 41. The liquid crystal display device of claim40, wherein each of the plurality of picture element regions includes aplurality of orientation-regulating regions, the plurality oforientation-regulating regions having the same direction of arrangementof the first, second and third regions.
 42. The liquid crystal displaydevice of claim 40, wherein each of the plurality of picture elementregions includes a first orientation-regulating region in which thefirst, second and third regions are arranged in this order in a firstdirection, and a second orientation-regulating region in which thefirst, second and third regions are arranged in this order in a seconddirection which is different from the first direction.
 43. The liquidcrystal display device of claim 42, wherein each of the plurality ofpicture element regions includes a plurality of at least one of thefirst orientation-regulating region and the secondorientation-regulating region.
 44. The liquid crystal display device ofclaim 42, wherein the first direction and the second direction areopposite to each other.
 45. The liquid crystal display device of claim44, each of the plurality of picture element regions further including athird orientation-regulating region in which the first, second and thirdregions are arranged in this order in a third direction which isdifferent from the first and second directions, and a fourthorientation-regulating region in which the first, second and thirdregions are arranged in this order in a fourth direction which isdifferent from the first, second and third directions, wherein the thirdand fourth directions are perpendicular to the first and seconddirections.
 46. The liquid crystal display device of claim 42, whereinthe first orientation-regulating region and the secondorientation-regulating region share at least one of the first region andthe third region.
 47. The device of claim 33, wherein a plurality of thepicture element regions are provided.
 48. The device of claim 33,wherein said boundary between the first region and the second region,and said boundary between the second region and the third region, areeach linear and are parallel to one another.
 49. The device of claim 40,wherein said boundary between the first region and the second region,and said boundary between the second region and the third region, areeach linear and are parallel to one another.
 50. The device of claim 33,further comprising: a third electrode in the pixel element region, thefirst electrode being provided on one side of the first substrate whichis closer to the liquid crystal layer than said third electrode; whereinin said second region the electric field is applied across the liquidcrystal layer by said third electrode and the second electrode and has asecond electric field strength which is smaller than the first electricfield strength, and wherein in the third region the electric fieldapplied across the liquid crystal layer by at least a slit and/oraperture region of the third electrode and the second electrode has athird electric field strength which is smaller than the second electricfield strength.